INTRODUCTION : Though India has been polio free since 2011, the number of children affected with paralysis has been steadily increasing. Acute flaccid paralysis can be caused by a number of reasons, of which one is polio. GBS, acute transverse myelitis, traumatic neuritis are some of the other causes.
In 2005, WHO recommended an operational rate of 2 cases of non- polio paralysis per 100,000 children < 15 years old. In 2013, this rate was 11.82/100,000 in India----almost 12 times higher than the internationally accepted norms.
We investigated the factors which could possibly explain this increasing trend of non polio paralysis in our country.

METHODS: We looked at the national data on polio and non polio numbers, doses of polio vaccine administered, population ,literacy and per capita income of all the states for a period of 14 years from 2000-2013. There are 28 states and 7 union territories in India ,all of which have different figures for these aforementioned factors. There were 525 data points that were analysed.
A multiple regression analysis adjusting for all these factors were done , results of which are presented in the table.
RESULTS: As you can see, number of polio doses was the only factor which showed a positive correlation with the non polio paralysis rate. For every additional dose of the polio vaccine given, the non polio paralysis increased by 1.3 cases/100,000.
Rest of the factors did not show any association.
(Explaining figure 1 ): The non-polio paralysis rate increased with an increasing number of polio vaccine doses given during 2000-2011, irrespective of time and region. The relationship is curvilinear with a more steep increase in non-polio paralysis beyond 6 doses of polio vaccine.
(Explaining fig 2) : Further, we looked at the cumulative effect of polio vaccine doses on the paralysis rate in each state. In the states of Uttar Pradesh and Bihar, we can see that the non- polio paralysis increased in proportion to the cumulative doses received. The paralysis is not much up to 6 doses but increases rapidly when more doses than that are used.
DISCUSSION:
1. Our results indicate that the incidence of non-polio AFP was strongly associated with the number of OPV doses delivered to the area. We also observed a dose response relation with cumulative doses over the years, which further strengthens the hypothetical relationship between polio vaccine and non-polio paralysis.
The fall in the non polio paralysis in Bihar and UP for the first time in 2012, with a decrease in the number of OPV doses delivered, is further corroborative evidence of a causative association between OPV doses and the NPAFP rate.
2. Follow-up of these cases of non-polio AFP is not done routinely. However a fifth of these cases of non-polio AFP in the state of Uttar Pradesh were followed-up after 60 days, in 2005. 35.2% were found to have residual paralysis and 8.5% had died (total residual paralysis or death 43.7%). There is thus an urgency to identify the reasons for the surge in non-polio paralysis numbers and take corrective measures immediately.
3. It is possible that factors that result in higher polio incidence in these states, like overcrowding and poor sanitation also promote spread of entero-pathogens which cause non polio paralysis. However poor sanitation by itself cannot explain why the incidence of non-polio paralysis should increase year after year in the same area, in proportion to doses of polio vaccine administered here.
4. Some have attributed this increase in non polio paralysis to good surveillance. A surveillance programme no matter how good, can only record every case of AFP, but it cannot exaggerate the numbers or explain the 25 to 35 fold increase in the non-polio AFP rate, as seen in the state of Bihar and UP (2010). In fact it is the states with the best health indicators and therefore presumably the best surveillance that have some of the lowest non-polio paralysis rates
5. The NPAFP may be considered as collateral damage in the effort to eradicate polio. It was hoped that after polio eradication the use of oral polio vaccine could be stopped and it could result in the reduction of NPAFP. However it is realised that this is unlikely to happen in the near future given the economic and logistical hurdles in switching to IPV
Therefore, our study would like to urge the experts to optimise the dosing schedule of OPV so as to prevent an inadvertent increase in non –polio paralysis in India.

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